The project will attempt to elucidate in fetal, neonatal, young and adult laboratory animals the hypothalamo-hypophysial mechanisms regulating target endocrine gland function. The nature and modus operandi of the interactions between the thyroid, adrenal and gonadal hormones and their analogues on the hypothalamic-pituitary units will also be explored. Research emphasis will be placed on problems of 1) maternal-fetal endocrine interrelations, 2) pituitary metabolism and trophic hormone secretion, 3) functional maturation of the neuroendocrine mechanisms, and 4) the competitive action of gonadal hormones on the pituitary-thyroid system. Experimental approaches will utilize manipulation of hypothalamic and pituitary functions by electrocoagulation, stimulation and hormone implantation and by surgical and chemical intervention at the target gland level in fetal, and postnatal, immature, adult and pregnant animals. The morphologic, physiologic and biochemical changes occurring in the various neuroendocrine systems will be evaluated through a battery of techniques (microscopy, radiometric and chemical procedures, bioassays, etc.).